1. Field of the Invention
The present invention relates to a thin film cell and a printed circuit board having the thin film cell incorporated therein and a method of fabricating the thin film cell and printed circuit board.
2. Description of the Related Art
An Mn dry cell and an Ni-Cd cell have conventionally been known as cells suitable for portable use. Each of these cells is composed of a positive electrode, a separator, an electrolyte, a negative electrode and a packaging material. By way of example, the method of fabricating an Ni-Cd cell will hereinafter be described. A nickel oxide and a cadmium compound are formed on separate nickel-made punched plate substrates. The thus-formed substrates are used as negative and positive electrodes respectively. Caustic potashes as an electrolytic material are implanted in a spacer made of a porous plastic which is held between both electrodes.
Thus, a nickel-made punched plate having strong rigidity is used as an electrode substrate and caustic potash solution is employed as an electrolyte in the conventional Ni-Cd cell. The following problems arise when trying to make thin flexible Ni-Cd cells or Mn dry cells.
(1) Inferiority in flexibility; PA1 (2) Failure to make thin enough; PA1 (3) Upon deformation of spacer, the spacer breaks and causes a short circuit; PA1 (4) There is a potential leakage of liquid; and PA1 (5) It is difficult to fabricate a cell having electrode patterns in a desired or large variety of shapes. PA1 forming at least one of the negative-polarity material, the electrolytic material and the positive-polarity material by using a screen printing process. PA1 In another aspect of this invention, there is provided a method for the fabrication of a printed circuit board with a thin film cell incorporated therein, comprising the steps of: PA1 forming a negative electrode on a substrate; PA1 forming lead terminals and wiring circuits which are to be connected to the negative electrode on the substrate; and PA1 forming an electrically-conductive polymer electrolyte, a positive electrode an an electric collector on the negative electrode successively; PA1 wherein at least one of the negative electrode, the electrolyte, the positive electrode and the collector, and the wiring circuits are formed by using a screen printing process. PA1 The above first-mentioned fabrication method permits the fabrication of thin and flexible cells of desired shapes in a continuous line. The above second-mentioned fabrication method also permits the fabrication of the printed circuit board with the thin film cells of desired shapes, which are to be incorporated therein.
Therefore, rigid-type shapes such as cylinder-type, button-type, coin-type and box-type shapes have principally been employed in the conventional cells. Thus, it has been considered not only difficult to realize thin and flexible cells but also to realize a design of cells in a variety of shapes.
It has also been considered difficult to mount a thin film cell on a printed circuit board (PCB) for the above-reasons.
The present invention has been completed with a view toward solving the foregoing problems.